As
of July 2011, with the Airport Express Line in service, the Delhi Metro
system comprises six lines with a total length of ~190 km and and 142
stations:

The
Red Line (initially
line 1)
extended its total length to 24.4 km (21 stations) with the eastern extension
to Dilshad Garden on 4 June 2008. The new section runs on a viaduct, parallel
to the mainline tracks.

The
previous extension brought the line length to 21.3 km (18 stations) on
31 March 2004
with the inauguration of the Inder Lok - Rithala section. The entire section is elevated and runs on a viaduct
constructed mostly on road medians.

The
first two sections of the Red Line
were opened on 25 December 2002 (Shahdara to Tis Hazari
- 8.3km, 6 stations) and 3 October 2003 (Tis Hazari to Inder
Lok - 4.1km, 4 stations) respectively. After two extensions, the line
is now 25 km long.

The

Yellow
Line (line 2) which was opened in two stages between
Vishwa Vidyalaya (Delhi University, North Campus) and Central
Secretariat, used to be underground for its entire 11 km length. The
route passes through the city centre, or the central business district
at Connaught Place. The stations along the route were built by cut-and-cover
technique except at Chawri Bazar where tunneling was used. Metro stations are located 12.85m below ground level except at the highly congested
Chawri Bazar station which is located at 20 m below ground. In
February 2009,

the

Yellow
Line was extended north to Jahangirpuri, including
the first four elevated stations on this line. The total length of the
Jahangirpuri - Central Secretariat is 17.4 km. In June 2010,
the first 14.5 km part of a southern extension was brought into service,
taking the Metro across the city border into Gurgaon. With the 12.5 km
missing section opened in September 2010, line 2 is now 45 km long.

The

Blue
Line (lines
3 & 4)
runs mostly elevated or at grade with a short underground section in central
New Delhi. It is currently (07/2011) about 60 km long.

The

Blue
Line
intersects with

the

Yellow
Line
at Connaught Place, but does not provide interchange with Line 1.

The Green
Line (line 5) is the first standard-gauge metro line in Delhi;
it is 15.1 km long (Inderlok to Mundka) and completely elevated.

The mostly
elevated Violet Line (line 6) opened
in two stages in 2010/2011.

The 22.5
km Airport Express Line (Orange Line)
opened in February 2011 after some delays and connects Indira Gandhi International
Airport to New Delhi railway station.

Rapid
Metro Gurgaon

Rapid Metro Gurgaon is a 5.1 km elevated standard-gauge mostly
single-track loop line, which runs from Sikanderpur Metro station on Delhi
Metro's Yellow Line, to serve Gurgaon CyberCity. The system was built
as Siemens turnkey project and started regular service on 14 Nov 2013.
(Official
Website)

Construction
of a second phase (7 km, 6 stations) along Golf Course Road began in 2013
for opening in July 2015.

History

The
planning for the Metro in Delhi had started in the 1950s. Numerous studies were
conducted for studying the feasibility of a rail based mass transit system.
The first steps towards the construction of the metro were only initiated
in 1995 when the Delhi Metro Rail Corporation (DMRC) was registered. Physical
work on the project started on October 1, 1998.